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The vehicle in question is the Lunokhod 1 rover, which landed in the Mare Imbrium aboard the Luna 17 lander in 1970. During the fortnight-long lunar days the machine was able to prowl about on electric drive, topping up its batteries using the fliptop solar panel mounted above its tub-like main body. During the long, chilly nights the lid would shut and the systems inside the tub were kept alive by a Polonium-210 radioisotope powered heater.

Lunokhod 1 stayed in touch with Soviet ground controllers for no less than 11 months, prowling the moon even as the US astronauts of Apollo 14 and 15 were driving about elsewhere in their manned moon buggies. However the robot crawler eventually ceased communications, and the project was officially terminated on October 4, 1971.

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A team of boffins in California, whose research involves measuring the Moon’s orbit with extreme precision in order to test Einstein’s theory of general relativity, have long made use of other lunar reflectors left by the Apollo programme.

“We yearned to find Lunokhod-1,” says Professor Tom Murphy, head of the moon-gazer team. “It would provide the best leverage for understanding the liquid lunar core, and for producing an accurate estimate of the position of the center of the moon—which is of paramount importance in mapping out the orbit and putting Einstein’s gravity to a test,” he adds.

Salvation came last month, when NASA released a tranche of detailed orbital photos of the Mare Imbrium, taken by its new Lunar Reconnaissance Orbiter (LRO) satellite as it made repeated passes just 30 miles above the surface. With these, it was possible to finally get a decent idea where the lost Lunokhod and its parent lander were.

“The recent images and laser altimetry from LRO provided coordinates within 100 meters, and then we were in business,” says Murphy.

Using the 3.5m telescope at Apache Point in New Mexico, Murphy and his colleagues were able at last to get a laser reflection back from the missing moon-prowler, getting its range to within a centimetre. A second reading less than 30 minutes later gave another line of position and pinned the machine down to within 10 metres. In time, Murphy believes he can refine this down to within a centimetre.